powerpc/85xx: Add phy nodes in SGMII mode for MPC8536/44/72DS & P2020DS

powerpc/85xx: Add phy nodes in SGMII mode for MPC8536/44/72DS & P2020DS

In SGMII riser card different PHY chip are used with different external
IRQ from eTSEC. To support PHY link state auto detect in SGMII mode we
should add another group of PHY nodes for SGMII mode.

For MPC8572DS IRQ6 is used for PHY0~PHY1, IRQ7 is used for PHY2~PHY3.
For MPC8544DS and MPC8536DS IRQ6 is used for PHY0~PHY1.
For P2020DS IRQ5 is used for PHY1~PHY2.

Signed-off-by: Li Yang <leoli@freescale.com>
Signed-off-by: Jia Hongtao <B38951@freescale.com>
Signed-off-by: Kumar Gala <galak@kernel.crashing.org>